Really disappointed with my cm- how do i let her down gently?

Have been using cm for 6 months. she does school run with 8 year old ds and has my 2 year dd 3 days a week. I found her great at first, supportive with my dd's speech probs and I liked her less formal approach. However, after pushing for a daily diary I have discovered dd has toast, crisps and fruit flakes for lunch all the time. Sometimes more fruit is offered but that is the general picture. CM never takes her ANYWHERE. Every day its playing inside all day. CM has 1 year old dd of her own plus 2 school age kids also hers. She minds another 1 year old and another school age one. What comes across is that she has far too much on her plate to really give dd much time and attention. DS says he is ignored as are all the older children.My ds has been very vocal, telling me cm shouts at dd, its not a great environment etc and cm has admitted of late that dd has been a handful.also when i turned on my phone this morning cm hasd text me to say her son was in hospital and she couldn't have dd today. No apology or anything. I understand she was stressed but still...So I am hunting for other cms right now. i know i prob have to give 1 months notice but when do i tell her- its going to be so awkward and i don't think I can stick another month with her...

Cm now knows. Had to do it by text in the end as she said she had prospective parents coming around and I didn't want her to lose business but again in the middle of the playground was not a great place to do it but neither was texting. she seems quiet and hurt. Just asked for it in writing and no more has been said apart from her saying she had just got a bigger car to do more trips and new children would never compromise current ones. I feel terrible but hopefully will all be ok in long run. Thanks everyone for your input.